Mitigation of salinity-induced negative impact on the growth and yield of wheat by plant growth-promoting rhizobacteria in naturally saline conditions

Salinity is one of the major environmental threats for successful crop production, hampering plant growth due to the osmotic effect and nutritional and hormonal imbalances. The application of naturally occurring plant growth-promoting rhizobacteria (PGPR) is an emerging technology aimed at ameliorating the negative impact of salinity. However, the results obtained in the laboratory can sometimes not be reproduced in the field. The aim of the study reported here was to evaluate the effect of PGPR inoculation on seed germination in a saline environment under axenic conditions and on enhancement of the growth and yield of wheat under natural salt-affected field conditions. Wheat seeds were inoculated with pre-isolated strains of Pseudomonas putida, Enterobacter cloacae, Serratia ficaria, and Pseudomonas fluorescens and sown at different salinity levels (1, 2, 3, 6, 9, 12, 15 dS m(-1)). Inoculation with these strains was found to enhance the germination percentage, germination rate, and index of wheat seeds up to 43, 51, and 123 %, respectively, over the uninoculated control at the highest salinity level. The potential of these PGPR for improving the growth and yield of wheat was also evaluated at two natural salt-affected sites. Inoculation with PGPR resulted a significant increase in the growth and yield parameters of wheat at both sites. The inoculated plants also improved the nutrient status of the wheat plants. The inoculated plants had low sodium and high nitrogen, phosphorus, and potassium contents. Our results show that such rhizobacterial strains may be used as an effective tool for enhancing plant growth under salinity stress and for maximizing the utilization of salt-affected soils.